Self-centering pneumatic grippers are already known which essentially comprise a support body, between coplanar, equidistant jaws which are guided and can be moved radially in the body between a closing position and an opening position, and a pneumatic piston accommodated in the body at right angles to the plane of the jaws and having a rod intended to control, by means of elbow-shaped relay rods, the simultaneous radial movements of the jaws when clamping and releasing a piece.
In the known pneumatic grippers of this type, the support body is made of metal and usually comprises at least two complementary elements, which together delimit a chamber for the piston for controlling the jaws. At least one of the elements of the body must be machined in order to produce seats and various accommodations for the rod of the piston, the jaws, the elbow-shaped relay rods, the pins for these rods, etc., the entire unit making the embodiment of the gripper rather complicated and difficult and its assembly laborious.